1. Field of the Invention
The invention relates to an adjustable lifting device for moving objects which may be heavy. More particularly, this invention relates to a lifting device such as a lift dolly or castor assembly which is adjustable such that it may be adapted for use with a variety of objects of different sizes, such as tools and tool stands, e.g. The invention further relates to an improved adjustable lifting device that includes a counterbalance to improve the performance of the lifting device.
2. Description of the Related Art
Often it is desirable to move objects, such as heavy equipment, in a timely fashion. Many devices are available for moving equipment on the factory floor or in a workshop. Some devices such as cranes are capable of transporting and lifting extremely heavy equipment. However, cranes are generally expensive and complex.
Alternatively, simple dollies that pivot about an axle are extremely portable and easy to use. However, these simple dollies are not capable of moving heavy equipment.
Therefore, it is desirable to provide a machine that is capable of lifting and moving heavy equipment in a simple method and timely fashion.
One attempt at providing such a lift dolly is disclosed in U.S. Pat. No. 5,876,173 English, incorporated by reference in its entirety herein. While the invention described in U.S. Pat. No. 5,876,173 is capable of lifting and transporting machine tools, it has been discovered that the latching mechanism may be difficult for a user to properly align, thus leading to an insecure lift.
Another attempt at providing such a lift dolly is disclosed in U.S. Pat. No. 5,957,649 to English, Stahl, and Hees, incorporated by reference in its entirety herein. While the invention described in U.S. Pat. No. 5,957,649 is also capable of lifting and transporting machine tools, it has also discovered that the toggle-type spring latching mechanism may prove to be unreliable to consistently latch and unlatch the dolly frames.
Therefore, it is also desirable to allow a user to align the latching mechanism in a robust, reliable manner. It is also desirable to provide a simple, robust, reliable latching mechanism which can be easily disengaged by a user to set the load down on the floor, without the use of power or hand tools.
For the foregoing reasons, there is a need for a lift dolly that is capable of lifting relatively heavy loads and transporting these loads in a secure fashion.
Additionally, it is desired that the described lift dolly be adjustable to fit a variety of objects such as tools. For instance, it is desirable that the same lift dolly be able to move a table saw, a drill press, or a wood lathe, e.g., at the user""s discretion. Thus, it is desirable that the frame of the lift dolly be adjustable.
Various attempts to provide the adjustable feature into a lift dolly are known. For instance, U.S. Pat. No. 5,957,649 to English discloses the use of telescoping tubes which create frame members 3, 4, 6, 7, and 8. Although acceptable for various applications, it was discovered that the frame members disclosed in English may fail to keep the frames level and the wheels perpendicular to the floor, which does not allow the wheels to pivot freely in all directions. Additionally, these frame members may fail when subjected to repeated loads from heavy objects because of the method by which the frame members are connected. Thus, there is a need of the lift dolly or caster to allow adjustment to permit the lift dolly or caster to fit a variety of different tools, while allowing the wheels to pivot freely in all directions. There is a need for these adjustable components that are connectable in a way that makes them more rugged and robust to be able to accommodate repeated, relatively heavy loads.
Some adjustable lifting devices may also tend to move from the stationary to object-moving position without notice: i.e. the weight of the caster frame may have a tendency to lift up on the tool as if it were set in a mobile position. Many attempts to overcome this issue are known. For instance, U.S. Pat. No. 5,876,173 to English discloses the use of connection rods 44 or energy absorbing gas struts to counter balance the weight of the frame. However, this English design may require a precision hinge mounting means to the frame, which may prove difficult to adapt the caster to different types of standard tool legstands. Thus, there is a need for a counterbalance for a tool stand that is easily adaptable to different sizes of standard tool legstands which prevents the lift dolly from lifting up on the tool itself. Additionally, it is desirable that the amount of tension holding be adjustable, and that the counterbalance be economical.
The claimed invention is directed overcoming, or at least minimizing, disadvantage of the prior art.
The invention relates to an adjustable apparatus for lifting and transporting an object. In some embodiments, the lift dolly employs a pedal latch mechanism that attaches to a U-bolt to securely lock the lift dolly in the position of lifting a heavy object. Use of this pedal latch securely provides a secure attachment of the frames of the lift dolly, thus ensuring that the heavy object will not be dropped. Further, once the object has been moved to a desired new location, a user may depress the pedal on the latching mechanism to easily lower the object. Because the pedal latch may be disengaged by the user""s foot pushing on the pedal, the user may easily and quickly disengage the lifting mechanism.
In some embodiments, an adjustable lift dolly for lifting and moving objects of different sizes is described having an adjustable first frame having an apex, a rear support assembly with an adjustable length, a plurality of first pivot ends connectable to the object, and a first pair of castors extending downwardly from the adjustable first frame; an adjustable second frame having a center support assembly with an adjustable length, a U-bolt support assembly having an adjustable length, a plurality of second pivot ends connectable to the object, and a second pair of castors extending downwardly from the second frame; a latching mechanism for releasably securing the adjustable first frame to the adjustable second frame, having a footplate attached to said first frame, the adjustable first frame being connectable to the adjustable second frame such that when a downward force is exerted on the apex of the adjustable first frame, the adjustable first frame pivots relative to the first pair of castors thus moving the first pivot ends of the adjustable first frame in an upward direction, said downward force on the adjustable first frame causing the adjustable first frame to exert a downward force on the center support assembly of the second frame, thus causing the second frame to pivot relative to the second pair of castors, thus moving the second pivot ends of the adjustable second frame in an upward direction, the upward movement of the of the first and second pivot ends thereby lever-lifting the object; and a foot pedal attached to the latching mechanism, the foot pedal being functionally associated with the latching mechanism such that by depressing the foot pedal, the latching mechanism disconnects the first frame from the second frame, wherein at least one of the lengths of the rear support assembly, center support assembly, or U-bolt support assembly is varied to accommodate objects of different sizes.
In some aspects the rear support assembly further comprises a rear member having two ends, and a plurality of first mounting members attached to the first frame, each end of the rear member being releaseably, telescopically mounted within one of the plurality of first mounting members such that the length of the rear support assembly may be varied. The rear members may be releaseably, telescopically mounted within one of the plurality of first mounting members by adjusting means for adjusting the length of the rear support assembly. The adjusting means may be an outward extruded hole in the plurality of first mounting members, a set screw and lock nut being threaded into the tapped, outward extruded hole to contact the rear member.
In some embodiments, the first adjustable frame has a plurality of first frame sides, each having an adjustable length; the plurality of first mounting members may be selectively secured to the first plurality of first frame sides by attachment means; and the attachment means further comprises each first frame side comprising a plurality of holes that mate with a hole with each of the first mounting members. An extension may be telescopically mountable within each first frame side.
In some embodiments, the center support assembly is a center support member having two ends; and a plurality of second mounting members attached to the second frame, each end of the center support member being releaseably, telescopically mounted within one of the plurality of second mounting members such that the length of the center support assembly may be varied.
In some embodiments, the U-bolt support assembly further comprises a U-bolt support member having two ends; and a plurality of third mounting members attached to the second frame, each end of the U-bolt support member being releaseably, telescopically mounted within one of the plurality of third mounting members such that the length of the U-bolt support assembly is adjustable. The second adjustable frame may have two frame sides, each having an adjustable length.
Also described is a counterbalance. The counterbalance may be a spring connected to the center support assembly and connectable to the object to bias the lift dolly weight from applying the upward movement to lever lift the object. The spring may be connectable to the object via an s-hook passing through one of a plurality of links in a chain, the tension in the spring being adjustable by moving the s-hook into another one of the plurality of links in the chain.
The invention also relates to a method of lifting and moving a first object from a first location to a second location and lifting and moving a second object from a third location to a fourth location.